In industrial production and scientific research,high temperature mea surement is often encountered, and optical fiber high temperature sensors have great market demand.We present and demonstrate a novel Michelson interferometer high temperature sensor.Michelson interferometer is fo rmed by femtosecond laser induced refractive index modification area in the core of the standard single mo de fiber and the end face of the fiber.The refractive index modification area is written directly by femtosecond laser in single fiber,which eliminates the required splicing or tapering process in traditional optical fibe r interferometer manufacturing and also significantly improves robustness.The experimental results show that the s ensor has good high temperature sensitivity,and the highest measurement temperature can reach 600℃.The sensor temperature sensitivity is 16.9pm/℃ in the high temperature and the linearity is 99.57%.The designed sensor has a very simple structure and can be used as a remote temperature measurement in oil and gas field development and oil detection.